Bilayer graphene (BLG) offers advantages that its more common form, monolayer graphene, does not. Most prominently, a dynamic, tunable bandgap can be readily induced in BLG from the near infrared to THz using only electrical fields. See Y. Lin and P. Avouris, Nano Letters 8, 2119 (2008); F. Xia et al., Nature Nanotechnoloqy 4, 839 (2009); and Y. Zhang et al., Nature 459, 820 (2009), which are incorporated herein by reference. This ability to tune the bandgap with only solid state technology enables faster, filter-less and more sensitive multispectral and hypertemporal imaging applications. Practically realizing these advantages, however, requires the ability to fabricate a tunable BLG device and a means to increase the absorption within this atomically thin material, which absorbs less than 5% of the incident light.
Therefore, a need remains for a BLG-based infrared photodetector that combines the tunability of BLG with a means to enhance the absorption of the BLG.